It is well known that the jackknifing of a tractor-trailer combination mostly takes place when an attempt is made to slow down or stop the tractor. The dynamics of each slow-down or stop changes each time, and the momentum of the tractor-trailer combination, road surface, weather, brake surfaces, distances involved and other variables are continually in flux. Due to this complexity tractor-trailer combinations are very frequently jackknifing, resulting in many serious accidents with great loss of life, maiming of many individuals, and costly material damage on the highways of the world. In particular excessive speed when turning curves is a primary cause of truck, or trailer-truck combination accidents, primarily because trucks generally have a higher center of gravity than passenger cars. Consequently when a truck, or trailer-truck combination turns a curve, particularly at high speed, the resultant centrifugal force may be sufficiently great to cause the truck to overturn, or cause jackknifing of a trailer-truck combination. It is, of course, a national objective to reduce motor-vehicle accidents of all kinds, which are statistically documented, for example, in the "Statistical Abstract of the United States, Section 22, Transportation, Land," 1982-1983 edition".
It is true that the driver of a truck can generally feel the action of the centrifugal force himself, and if he does, he would under normal circumstances slow down, so as to reduce the centrifugal force, equal to v.sup.2 /r, where v is the speed of the vehicle, and r is the radius of curvature of the road. Nevertheless, one has to reckon with the fact that occasionally a driver may be less than responsible, particularly if he is under the influence of any drinks or drugs. In such case it would be desirable to have an automatic override system take over, which monitors any incipient danger of the vehicle being overturned, and automatically takes corrective action.
An attempt to remedy the jacknifing of a track-trailer combination is described by Beck, U.S. Pat. No. 4,346,910. Beck uses a structure secured to the vehicle, including mechanical means, that is operative when activated to extend rigidly between the vehicle and the trailer. An activation means is secured to the vehicle and is operative to activate the mechanical means at a pre-specified condition during the operation of the vehicle. A generally similar device is also disclosed by the applicant of the present invention in U.S. Pat. No. 3,507,517. The aforesaid prior art has the disadvantage that it generally detects the aforesaid disadvantageous conditions too late, and furthermore is only applicable to a truck-trailer combination, but not to a vehicle only.
Some of the newer luxury cars are being outfitted with computer-assisted devices which have primarily been developed to sense skid, and which have a mechanism to selectively act on the brakes of the vehicle, or possibly even on the gas pedal and the steering wheel. The primary object here has been to develop an anti-skid system, with less emphasis on countering any incipient overturning moment which may manifest itself due to the aforesaid causes of both excessive vehicle speed, and a high degree of road curvature. Also systems of the prior art are generally not suited for being retrofitted to cars of an earlier vintage.